JPH0257225B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel supply control system for a variable bench lily type carburetor.

When the engine is started and the engine is being rotated by the starter motor when the engine temperature is low, a rich air-fuel mixture with an air-fuel ratio of about 1 to 2 is required;
It should be increased to about ~10. For this purpose, conventionally, for example, as described in Japanese Utility Model Application Publication No. 56-103650, an air bleed control valve that responds to the negative pressure in the intake passage downstream of the throttle valve is provided in the air bleed passage. By closing the air bleed control valve, a rich air-fuel mixture is formed, and when the engine starts operating on its own, the air bleed control valve is opened to increase the air-fuel ratio. Furthermore, as described in, for example, Japanese Utility Model Application No. 56-99042, an atmosphere communication control valve is provided to control the communication of the negative pressure chamber of the suction piston with the atmosphere, and this atmosphere communication control valve is used to control the intake air downstream of the throttle valve. It is controlled by the negative pressure in the passage, and during cranking, the negative pressure chamber of the suction piston is communicated with the atmosphere to form a rich mixture, and when the engine starts operating on its own, communication with the atmosphere is cut off to maintain the air-fuel ratio. I'm trying to make it bigger.

However, there is a considerable difference between the required air-fuel ratio during cranking and the required air-fuel ratio when the engine starts operating on its own, so either air bleed control or atmospheric communication control of the suction piston negative pressure chamber must be performed. However, it is difficult to create this required air-fuel ratio difference, and in order to create this required air-fuel ratio difference, it is necessary to perform these air bleed controls and the communication of the suction piston negative pressure chamber with the atmosphere at the same time. In this case, if the air bleed control valve and the atmosphere communication control valve are provided independently and attempted to be controlled independently, there is a problem that not only the size of the carburetor increases, but also the number of parts increases.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel supply control device for a variable vent lily type carburetor, which has a simple structure and can perform air bleed control and atmospheric communication control of a suction piston negative pressure chamber at the same time.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, 1 is a carburetor main body, 2 is an intake passage extending vertically, 3 is a suction piston that moves laterally within the intake passage 2, and 4 is attached to the tip surface of the suction piston 3. 5 is a spacer fixed on the inner wall surface of the intake passage 2 facing the tip surface of the suction piston 3;
Reference numeral 6 indicates a throttle valve provided in the intake passage 2 downstream of the suction piston 3, 7 indicates a carburetor float chamber, and a bench lily portion 8 is formed between the front end surface of the suction piston 3 and the spacer 5. Ru.
A hollow cylindrical casing 9 is fixed to the carburetor body 1, and a guide sleeve 10 extending in the axial direction of the casing 9 inside the casing 9 is attached. A bearing 12 with a number of balls 11 is inserted into the guide sleeve 10,
Further, the outer end surface of the guide sleeve 10 is closed by a blind cover 13. On the other hand, a guide rod 14 is fixed to the suction piston 3.
is inserted into the bearing 12 so as to be movable in the axial direction of the guide rod 14. Since the suction piston 3 is thus supported by the casing 9 via the bearing 12, the suction piston 3 can move smoothly in its axial direction. Casing 9
The interior of the is a negative pressure chamber 1 by a suction piston 3.
5 and an atmospheric pressure chamber 16, and a compression spring 17 is inserted into the negative pressure chamber 15 to constantly press the suction piston 3 toward the bench lily portion 8. The negative pressure chamber 15 is connected to the bench lily section 8 through a suction hole 18 formed in the suction piston 3, and the atmospheric pressure chamber 16 is connected to the suction piston 3 upstream through an air hole 19 formed in the carburetor body 1. The intake passage 2 is connected to the inside of the intake passage 2.

On the other hand, a fuel passage 20 extending in the axial direction of the needle 4 is formed in the carburetor body 1 so that the needle 4 can enter therein, and a metering jet 21 is provided within this fuel passage 20. The fuel passage 20 upstream of the metering jet 21 has a fuel pipe 22 extending downward.
is connected to the float chamber 7 via the float chamber 7.
The fuel inside is sent into the fuel passage 20 via this fuel pipe 22. Furthermore, a hollow cylindrical nozzle 23 arranged coaxially with the fuel passage 20 is fixed to the spacer 5 . This nozzle 23 protrudes into the bench lily portion 8 from the inner wall surface of the spacer 5, and the upper half of the tip of the nozzle 23 further protrudes from the lower half toward the suction piston 3.
Needle 4 is connected to nozzle 23 and metering jet 21
The fuel is metered by the annular gap formed between the needle 4 and the metering jet 21 and then fed into the intake passage 2 from the nozzle 23.

As shown in FIG. 1, an annular air passage 24 is formed around the metering jet 12, and a plurality of air bleed holes 25 that communicate the annular air passage 24 with the inside of the metering jet 21 are formed around the metering jet 2.
1 is formed on the inner circumferential wall surface of No. 1. Annular air passage 24
is connected to an air bleed passage 26 formed within the carburetor body 1. In addition, an auxiliary air bleed hole 2 is provided on the upper wall surface of the fuel passage 20 downstream of the metering jet 21.
7 is formed, and this auxiliary air bleed hole 27 is connected to the air bleed passage 26. On the other hand, the needle 4 has a small diameter portion 28 approximately at its center, and this small diameter portion 28 is inserted into the metering jet 21 when the suction piston 3 is most closed off to the intake passage 2, as shown in FIG. To position.

As shown in FIG. 1, the upper end of the spacer 5 has a raised wall 2 projecting horizontally into the intake passage 2
9 is formed, and the flow rate is controlled between this raised wall 29 and the tip of the suction piston 3. When engine operation is started, air flows downward in the intake passage 2. At this time, since the air flow is restricted between the suction piston 3 and the raised wall 29, negative pressure is generated in the bench lily portion 8, and this negative pressure is guided into the negative pressure chamber 15 through the suction hole 18. The suction piston 3 is arranged so that the pressure difference between the negative pressure chamber 15 and the atmospheric pressure chamber 16 becomes a substantially constant pressure determined by the spring force of the compression spring 17, that is, so that the negative pressure inside the bench lily portion 8 becomes substantially constant. Moving.

Air bleed passage 26 as shown in FIG.
is connected to the throttle valve opening control valve 30 and the negative pressure control valve 31. Throttle valve opening control valve 30
The housing 32 has a circular hole 33 extending in the longitudinal direction and a wax valve 34, and a push rod 3 driven by the wax valve 34 is inserted into the circular hole 33.
5 is slidably inserted. This push rod 35 has a pair of enlarged portions 36, 37 spaced apart from each other.
The inner end 38 of the enlarged portion 37 is formed into a conical shape. The outer end of the enlarged portion 37 projects outward from the housing 32, and a disk-shaped head 39 is integrally formed at the distal end of the enlarged portion 37. Also, the ampulla 37
The protruding outer end of is surrounded by a sealing member 40 fixed to the housing 32. On the other hand, a large diameter hole 41 is formed in the housing 32, and this large diameter hole 4
1, a wax valve holder 42 is fitted inside. An O-ring 43 is inserted between the wax valve holder 42 and the inner peripheral surface of the large diameter hole 41. Furthermore, large diameter hole 4
A plug 44 is screwed into the inside of the wax valve holder 42 through a gasket 45, and the wax valve 34 is attached to the wax valve holder 42.
The plug 44 is fixedly held in the housing 32 via the plug 44 . Wax valve holder 42 and plug 4
An engine cooling water introduction chamber 46 is formed between 4 and a cooling water supply chamber 47 is connected to this cooling water introduction chamber 46. Cooling water introduction chamber 4 via cooling water supply pipe 47
The cooling water supplied into the cooling water pump 6 heats the wax valve 34 and is then discharged from the cooling water discharge hole 48.

As shown in Fig. 2, the throttle valve opening control valve 3
The housing 32 of No. 0 is fixed to the carburetor main body 1 with three bolts 49. Referring to FIGS. 2 to 5, a bolt 50 serving as a pivot is screwed into the housing 32, and a cam 51 and a lever 52 are rotatably attached to the bolt 50. The lever 52 includes an L-shaped portion 52b spaced from an intermediate portion 52a thereof;
2a and the L-shaped portion 52b are connected to each other by a U-shaped portion 52c. Intermediate portion 52a and L
The pin 5 extends through the shape portion 52b.
3 is fixed, and a roller 54 is rotatably mounted on this pin 53. Tip 52 of lever 52
A tension spring 56 is stretched between the pin 55 fixed to the housing 32 and the tension spring 56.
The spring force keeps the roller 54 in constant pressure contact with the disc-shaped head 39 of the push rod 35. On the other hand, an arm portion 52e is integrally formed at the tip of the L-shaped portion 52b of the lever 52, and an arm portion 51a facing the arm portion 52e is also integrally formed at the end of the cam 51. An adjusting screw 57 is inserted into a hole (not shown) formed in the arm portion 51a of the cam 51.
The tip of this adjustment screw 57 is connected to the arm 5 of the lever 52.
It is screwed onto 2e. Therefore, by turning this adjusting screw 57, the relative position of the lever 52 and the cam 51 can be adjusted. Note that these arm portions 5
A compression spring 58 for preventing the adjustment screw 57 from loosening is inserted between the arm portion 1a and the arm portion 52e. The rotational force of the lever 52 is transmitted to the cam 51 via the adjustment screw 57, and when the lever 52 is rotated clockwise in FIG. 2, the cam 51 is also rotated clockwise. On the other hand, as shown in FIG. 2, a lever 61 is fixed to the valve shaft 60 of the throttle valve 6, and a cam 51 is attached to the tip of the lever 61.
A pin 63 that can engage with the cam surface 62 of is fixed. As can be seen from FIG. 2, the radius r of the cam surface 62 measured from the bolt 50 gradually decreases in the counterclockwise direction.

FIG. 2 shows a state where the engine temperature is low, and at this time the throttle valve 6 is held open by the action of the cam 51. When the engine is started and the engine cooling water temperature rises, the wax valve 34 moves the push rod 35 to the left in FIG. As a result, since the lever 52 is rotated counterclockwise, the cam 51 is also rotated counterclockwise, and thus the throttle valve 6
will be gradually closed. As mentioned above, the disk-shaped head 39 of the push rod 35
Since a roller 54 is provided between the lever 52 and the lever 52, when the push rod 35 moves to the left in FIG. 2, the lever 52 rotates smoothly.

Returning to FIG. 1 again, an atmospheric pressure chamber 70 is formed in the circular hole 33 of the throttle valve opening control valve 30 between a pair of enlarged portions 35 and 36, and this atmospheric pressure chamber 70 has an atmospheric communication hole 71. It is constantly communicated with the atmosphere through the Further, inside the housing 32, there is a first port 72 that is always open into the atmospheric pressure chamber 70, and an enlarged portion 36.
A second port 73 whose communication to the atmospheric pressure chamber 70 is controlled by the
A third port 74 is formed in which communication into the third port 74 is controlled, and a throttle 75 is inserted into the third port 74. On the other hand, in the negative pressure control valve 31, a piston 80 constituting a first on-off valve and a piston 81 constituting a second on-off valve are slidably inserted therein. Aperture hole 82
A partition wall 83 having a diameter is fitted. A first negative pressure chamber 84 is formed between the piston 80 and the partition 83, and a compression spring 85 is inserted between the piston 80 and the partition 83. This first negative pressure chamber 84 is connected to the throttle valve 6
It is connected via a negative pressure conduit 87 to a negative pressure port 86 that opens into the downstream intake passage 2 . piston 80
are a pair of piston members 80a spaced apart from each other,
80b, these piston members 80
A pair of ports 89 and 90 open into the internal chamber 88 formed between a and 80b. The port 89 is connected via a conduit 92 to a port 91 that opens into the negative pressure chamber 15, and the port 90 is connected to the second port 73 of the throttle valve opening control valve 30. On the other hand, a second negative pressure chamber 93 is formed between the piston 81 and the partition 83, a compression spring 94 is inserted between the piston 81 and the partition 83, and a seal member 95 is fixed to the top surface of the piston 81. . Further, the housing of the negative pressure control valve 31 is formed with a port 97 that is always open in the internal chamber 96 between the inner wall surface of the housing and the top surface of the piston 81 . It is coupled to port 72 . Furthermore, a port 98 whose opening and closing are controlled by a seal member 95 of the piston 81 is formed in the housing of the negative pressure control valve 31, and a throttle 99 is inserted into this port 98. This port 98 and the third port 74 of the throttle valve opening control valve 30 are connected to the air bleed passage 26.

FIG. 1 shows a state where the engine temperature is low and the engine is stopped, and at this time the suction piston 3 is located at the position that most closes the intake passage 2. Next, when the starter motor is rotated to start the engine, since the negative pressure in the intake passage 2 downstream of the throttle valve 6 is small, the pistons 80 and 81 of the negative pressure control valve 31 are at the positions shown in FIG. It is in. Therefore, at this time, the negative pressure chamber 15 is in communication with the atmosphere via the negative pressure control valve 31 and the throttle valve opening control valve 30, so the inside of the negative pressure chamber 15 is at atmospheric pressure, and therefore the suction piston 3
is held in the position shown in FIG. Since the small diameter portion 28 of the needle 4 is thus located within the metering jet 21, the area of the annular gap formed between the needle 4 and the metering jet 21 is large, and a large amount of fuel is supplied from the nozzle 23 into the intake passage 2. Ru. on the other hand,
At this time, the port 98 of the negative pressure control valve 31 is closed by the seal member 95 of the piston 81.
Since the third port 74 of the throttle valve opening control valve 30 is slightly opened, a very small amount of air is supplied from the air bleed holes 25 and 27. Therefore, when the engine is being rotated by the starter motor, an extremely rich air-fuel mixture is supplied into the engine cylinders.

When the engine starts operating on its own, the negative pressure in the intake passage 2 downstream of the throttle valve 6 increases, so the piston 80 of the negative pressure control valve 31 immediately releases the compression spring 85.
, and as a result port 89,9
0 is closed by the piston part 80a of the piston 80. In this way, the negative pressure inside the bench lily portion 8 acts on the inside of the negative pressure chamber 15 through the suction hole 18, so that the suction piston 3 moves to the left. As a result, the area of the annular gap formed between the needle 4 and the metering jet 21 due to the exit of the small diameter portion 28 of the needle 4 from within the metering jet 21 is reduced, and thus the amount of fuel supplied from the nozzle 29 is reduced. It will be done. On the other hand, even if the negative pressure downstream of the throttle valve 6 becomes large, the second
The negative pressure in the negative pressure chamber 92 does not increase immediately because the throttle hole 82 is provided.
continues to be closed by the seal member 95 of the piston 81 for a while. After the engine starts operating on its own, the negative pressure in the second negative pressure chamber 93 increases, so the piston 81 gradually moves to the left against the spring force of the compression spring 94. Port 98 is gradually opened. Therefore, since the amount of air supplied from the air bleed holes 25, 27 gradually increases, the air-fuel mixture supplied into the engine cylinder becomes gradually leaner. In this way, when the engine starts to run on its own, the amount of fuel supplied from the nozzle 23 is gradually reduced, so the air-fuel mixture does not become too lean immediately after the engine starts to run on its own, and the air-fuel mixture does not become too lean for a while after the engine starts to run on its own. The air-fuel mixture does not become too rich when the engine is at ease. Therefore, stable starting of the engine can be ensured.

Next, when the engine cooling water temperature rises, the wax valve 3
As the push rod 35 is moved to the left by the action of 4, the opening area of the third port 74 gradually increases, and as a result, the air bleed hole 25,
Since the amount of air supplied from 27 gradually increases, the air-fuel mixture supplied into the engine cylinder becomes gradually leaner. When the warm-up operation is completed, the third port 74 is fully opened, so that an air-fuel mixture with a predetermined air-fuel ratio is supplied into the engine cylinder. On the other hand, when the warm-up operation is completed, the second port 73 is blocked by the enlarged portion 36 of the push rod 35. Therefore, when the engine is started with a high engine temperature, negative pressure acts in the negative pressure chamber 15, so that the needle 4
The small diameter portion 28 of the nozzle immediately separates from the metering jet 21, so that less fuel is supplied from the nozzle 23 than when the engine is cold started. On the other hand, immediately after the engine starts operating on its own, the port 98 of the negative pressure control valve 31 is closed by the seal member 95 of the piston 81, so the amount of supplied fuel temporarily increases, and the engine It is possible to prevent the engine from stopping immediately after starting, and it is also possible to prevent misfire from occurring some time after starting the engine.

Another embodiment of the negative pressure control valve 31 is shown in FIG.
In this embodiment, the second negative pressure chamber 93 is connected to the negative pressure port 86 (FIG. 1) through the negative pressure conduit 87, and the first negative pressure chamber 84 is connected to the first negative pressure chamber 9 through the throttle hole 82.
3. Therefore, in this embodiment, when the engine starts operating under its own power, the sealing member 95 of the piston 81 immediately opens the port 98, so that the amount of fuel supplied from the nozzle 23 is reduced. On the other hand, immediately after the engine starts operating on its own, the negative pressure chamber 15 is communicated with the atmosphere via the negative pressure control valve 31, so the suction piston 3 is
The piston 80 is held in the position shown in the figure, and after a while after the engine starts operating on its own, the piston 80 moves to the right and closes the ports 89 and 90, so that a vacuum is created in the negative pressure chamber 15 of the suction piston 3. pressure is introduced.
Since the suction piston 3 thus moves to the left, the amount of fuel supplied from the nozzle 23 is reduced. Therefore, in this embodiment as well, it is possible to prevent the engine from stopping immediately after the engine is started, and it is also possible to prevent a misfire from occurring some time after the engine is started.

As described above, according to the present invention, the first on-off valve and the second on-off valve are arranged in a common negative pressure control valve housing, and the first on-off valve is disposed in the partition wall formed in the negative pressure control valve housing. By providing three roles: supporting the compression spring for pressing the valve, supporting the compression spring for pressing the second opening/closing valve, and forming the throttle hole, the suction piston and air bleed. The structure of the negative pressure control valve for simultaneously controlling both is extremely simplified, and the number of parts can be further reduced.

[Brief explanation of drawings]

Fig. 1 is an overall view of the carburetor according to the present invention, Fig. 2 is an overall view of the throttle valve opening control mechanism, Fig. 3 is a plan view taken along the arrow in Fig. 2, and Fig. 4 is Fig. 3. Figure 5 is a side view taken along the arrow.
A cross-sectional view taken along the - line in the figure, Figure 6 is the first
FIG. 3 is a side cross-sectional view of another embodiment of the negative pressure control valve shown in the figure. 3... Suction piston, 6... Throttle valve, 30... Throttle opening control valve, 31... Negative pressure control valve, 34... Wax valve, 35... Push rod, 80, 81... Piston, 82... ...Aperture hole.

Claims (1)

[Claims] 1. A suction piston that changes the area of the bench lily in response to the amount of intake air, a needle connected to the suction piston, a fuel passage extending in the axial direction of the needle so that the needle can enter, and the fuel A variable vent valve carburetor having a metering jet disposed in a passageway and cooperating with the needle, and further comprising an air bleed passageway for supplying air into the fuel passageway. The chamber is connected to the atmosphere via a first on-off valve, and the air bleed passage is connected to the atmosphere via a second on-off valve, and the first on-off valve and the second on-off valve are formed from a piston and spaced apart from each other. are arranged coaxially in a common negative pressure control valve housing with the first on-off valve and the second on-off valve separated from each other, a partition is provided between the first on-off valve and the second on-off valve, and a first negative pressure chamber is defined between the first on-off valve and the partition. A second on-off valve is formed between the second on-off valve and the partition wall.
Further, a compression spring for pressing the first on-off valve is inserted between the first on-off valve and the partition, and a compression spring for pushing the second on-off valve is inserted between the second on-off valve and the partition. A throttle hole is formed in the partition wall to communicate the first negative pressure chamber and the second negative pressure chamber, and one of the first negative pressure chamber and the second negative pressure chamber is connected to the intake passage downstream of the throttle valve. The first on-off valve and the second on-off valve are controlled by the negative pressure in the intake passage downstream of the throttle valve, and the first on-off valve is opened when the negative pressure is smaller than a predetermined negative pressure. to communicate the negative pressure chamber of the suction piston with the atmosphere and close the second on-off valve to shut off the air bleed passage, and when the negative pressure is greater than a predetermined negative pressure, the first The on-off valve is closed to cut off communication between the negative pressure chamber of the suction piston and the atmosphere, and the second on-off valve is opened to allow the air bleed passage to communicate with the atmosphere, and the negative pressure is set in advance. For a while after the negative pressure becomes larger than the negative pressure, the restricting action of the restricting hole formed in the partition wall delays the action of blocking communication between the negative pressure chamber of the suction piston and the atmosphere, or air bleed occurs. A fuel supply control device for a variable bench lily type carburetor in which the atmospheric communication effect of the passage is delayed.